All of the patents cited throughout this specification are hereby entirely incorporated herein.
Quaternary ammonium compounds are well known as complexing agents for certain compounds, such as anionic dyes. For example, U.S. Pat. No. 5,059,244, to King, discloses an aqueous solution of anionic dyes and an ethoxylated triethanolamine. This composition is useful as an ingredient within ink formulations and as an agent for temporarily tinting textile fibers. Quaternary ammonium compounds have been disclosed as useful auxiliary agents for printing on fiber materials. For example, U.S. Pat. No. 3,785, 767, to Hildebrand, discloses a pad-steaming process for the continuous dyeing and printing of fiber material with a formulation containing anionic dyes and amine salts. Other pertinent teachings include U.S. Pat. No. 4,563,190, to Topfl, which discloses a dyeing assistant formulation for anionic dyes containing quaternary ammonium compounds that contain at least one basic nitrogen atom to which are attached at least one polyglycol ether chain; U.S. Pat. No. 4,935,033, to Mosimann et al., which discloses a dyeing method for natural polyamide fibers using reactive dyes and a dyeing assistant agent containing a quaternary ammonium compound; and U.S. Pat. No. 4,369,041, to Dvorsky et al., discloses a technique for printing textiles involving exposing the textile to the action of quaternary ammonium compounds before or during the dyeing or printing with acid dyes. Furthermore, Aston et al., U.S. Pat. No. 5,403,358, discloses a pretreatment composition for ink jet which comprises a quaternary ammonium compound and a reactive dye. Such anionic dyes and quaternary ammonium compounds also find application in other areas, for instance: U.S. Pat. No. 4,459,130, to Helling et al., discloses a dye preparation which is consisted of an acid dye and a basic carrier which contains quaternary ammonium or phosphonium groups; and U. S. Pat. No. 5,266,077, to Auten et al., discloses a method for tinting a hydrophilic contact lens through the action of a quaternary ammonium compound as a dye complexing agent.
However, there is no specific teaching of a water-soluble, substantially salt-free complex of an optical brightener and a quaternary ammonium compound. The closest prior art, U.S. Pat. No. 4,888,128, to Koll et al., discloses water-insoluble brightener salts which are products of the reaction between anionic cellulose fluorescent brighteners and quaternary ammonium compounds as whiteners for paper-coating slips. There is no disclosure nor fair suggestion of the inventive substantially salt-free water-soluble optical brightening complexes whatsoever anywhere within patentee's teachings. Water solubility is of utmost importance to the inventive complex as such a property provides substantial benefits in dispensability and compatibility within various substrates.
It has been found that the complexation of an anionic, preferably sulfonated, optical brightener with specific types of quaternary ammonium compounds and the subsequent removal of substantially all the excess salt formed during such a reaction produces a water-soluble compound which possesses the highly desired and unexpected characteristics as listed above. Therefore, through the utilization of inexpensive reactions and quaternary ammonium compounds, the cost of providing a highly compatible, soluble, dispensable, and wash- and light-fast optical brightener compound with an affinity for myriad substrates can be greatly reduced. Therefore, it has been found that water-soluble substantially salt-free optical brightener/quaternary ammonium colorant complexes provide a cost-effective method of providing a great deal of highly desirable and beneficial brightening properties to many different substrates.
When placed in a complexing solution, the anionic brighteners and the quaternary ammonium compounds show great affinity for one another such that upon disassociation with their respective cations and/or counter ions, the complexation of the brightener and quat drives the formation of the excess salts comprised of the free cations and counter ions. Once the salts are formed, they are easy to remove through filtration, phase separation, or extraction techniques. Such a salt removal ensures the brightener and quat will remain in a complex together rather than potentially reacting with free cation and/or counter ion upon disassociation within the resultant optical brightener solution. Thus, the desired properties are obtained with a greater amount of the brightener/quat complex and a much lower amount of residual salt.